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Mon, 11 May 2020 05:14:06 -0700 (PDT) From: Paul Durrant X-Google-Original-From: "Paul Durrant" Reply-To: To: "'Denis Kirjanov'" Cc: , , , , References: <1589192541-11686-1-git-send-email-kda@linux-powerpc.org> <1589192541-11686-3-git-send-email-kda@linux-powerpc.org> <000c01d62787$f2e59a10$d8b0ce30$@xen.org> In-Reply-To: Subject: RE: [PATCH net-next v9 2/2] xen networking: add XDP offset adjustment to xen-netback Date: Mon, 11 May 2020 13:14:05 +0100 Message-ID: <000e01d6278d$ab04aa50$010dfef0$@xen.org> MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Mailer: Microsoft Outlook 16.0 Content-Language: en-gb Thread-Index: AQIU9PmTVpNq2fLG8JgzWe5HwULahQDzXzdtAsUqzywBx8zP6af5Llyw Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org > -----Original Message----- > From: Denis Kirjanov > Sent: 11 May 2020 13:12 > To: paul@xen.org > Cc: netdev@vger.kernel.org; brouer@redhat.com; jgross@suse.com; wei.liu@kernel.org; > ilias.apalodimas@linaro.org > Subject: Re: [PATCH net-next v9 2/2] xen networking: add XDP offset adjustment to xen-netback > > On 5/11/20, Paul Durrant wrote: > >> -----Original Message----- > >> From: Denis Kirjanov > >> Sent: 11 May 2020 11:22 > >> To: netdev@vger.kernel.org > >> Cc: brouer@redhat.com; jgross@suse.com; wei.liu@kernel.org; paul@xen.org; > >> ilias.apalodimas@linaro.org > >> Subject: [PATCH net-next v9 2/2] xen networking: add XDP offset adjustment > >> to xen-netback > >> > >> the patch basically adds the offset adjustment and netfront > >> state reading to make XDP work on netfront side. > >> > >> Signed-off-by: Denis Kirjanov > >> --- > >> drivers/net/xen-netback/common.h | 2 ++ > >> drivers/net/xen-netback/netback.c | 7 +++++++ > >> drivers/net/xen-netback/rx.c | 7 ++++++- > >> drivers/net/xen-netback/xenbus.c | 28 ++++++++++++++++++++++++++++ > >> 4 files changed, 43 insertions(+), 1 deletion(-) > >> > >> diff --git a/drivers/net/xen-netback/common.h > >> b/drivers/net/xen-netback/common.h > >> index 05847eb..4a148d6 100644 > >> --- a/drivers/net/xen-netback/common.h > >> +++ b/drivers/net/xen-netback/common.h > >> @@ -280,6 +280,7 @@ struct xenvif { > >> u8 ip_csum:1; > >> u8 ipv6_csum:1; > >> u8 multicast_control:1; > >> + u8 xdp_enabled:1; > >> > >> /* Is this interface disabled? True when backend discovers > >> * frontend is rogue. > >> @@ -395,6 +396,7 @@ static inline pending_ring_idx_t > >> nr_pending_reqs(struct xenvif_queue *queue) > >> irqreturn_t xenvif_interrupt(int irq, void *dev_id); > >> > >> extern bool separate_tx_rx_irq; > >> +extern bool provides_xdp_headroom; > >> > >> extern unsigned int rx_drain_timeout_msecs; > >> extern unsigned int rx_stall_timeout_msecs; > >> diff --git a/drivers/net/xen-netback/netback.c > >> b/drivers/net/xen-netback/netback.c > >> index 315dfc6..6dfca72 100644 > >> --- a/drivers/net/xen-netback/netback.c > >> +++ b/drivers/net/xen-netback/netback.c > >> @@ -96,6 +96,13 @@ > >> module_param_named(hash_cache_size, xenvif_hash_cache_size, uint, 0644); > >> MODULE_PARM_DESC(hash_cache_size, "Number of flows in the hash cache"); > >> > >> +/* The module parameter tells that we have to put data > >> + * for xen-netfront with the XDP_PACKET_HEADROOM offset > >> + * needed for XDP processing > >> + */ > >> +bool provides_xdp_headroom = true; > >> +module_param(provides_xdp_headroom, bool, 0644); > >> + > >> static void xenvif_idx_release(struct xenvif_queue *queue, u16 > >> pending_idx, > >> u8 status); > >> > >> diff --git a/drivers/net/xen-netback/rx.c b/drivers/net/xen-netback/rx.c > >> index ef58870..c97c98e 100644 > >> --- a/drivers/net/xen-netback/rx.c > >> +++ b/drivers/net/xen-netback/rx.c > >> @@ -33,6 +33,11 @@ > >> #include > >> #include > >> > >> +static int xenvif_rx_xdp_offset(struct xenvif *vif) > >> +{ > >> + return vif->xdp_enabled ? XDP_PACKET_HEADROOM : 0; > >> +} > >> + > >> static bool xenvif_rx_ring_slots_available(struct xenvif_queue *queue) > >> { > >> RING_IDX prod, cons; > >> @@ -356,7 +361,7 @@ static void xenvif_rx_data_slot(struct xenvif_queue > >> *queue, > >> struct xen_netif_rx_request *req, > >> struct xen_netif_rx_response *rsp) > >> { > >> - unsigned int offset = 0; > >> + unsigned int offset = xenvif_rx_xdp_offset(queue->vif); > >> unsigned int flags; > >> > >> do { > >> diff --git a/drivers/net/xen-netback/xenbus.c > >> b/drivers/net/xen-netback/xenbus.c > >> index 286054b..d447191 100644 > >> --- a/drivers/net/xen-netback/xenbus.c > >> +++ b/drivers/net/xen-netback/xenbus.c > >> @@ -393,6 +393,20 @@ static void set_backend_state(struct backend_info > >> *be, > >> } > >> } > >> > >> +static void read_xenbus_frontend_xdp(struct backend_info *be, > >> + struct xenbus_device *dev) > >> +{ > >> + struct xenvif *vif = be->vif; > >> + unsigned int val; > >> + int err; > >> + > >> + err = xenbus_scanf(XBT_NIL, dev->otherend, > >> + "feature-xdp", "%u", &val); > >> + if (err != 1) > >> + return; > >> + vif->xdp_enabled = val; > >> +} > >> + > >> /** > >> * Callback received when the frontend's state changes. > >> */ > >> @@ -417,6 +431,11 @@ static void frontend_changed(struct xenbus_device > >> *dev, > >> set_backend_state(be, XenbusStateConnected); > >> break; > >> > >> + case XenbusStateReconfiguring: > >> + read_xenbus_frontend_xdp(be, dev); > > > > I think this being the only call to read_xenbus_frontend_xdp() is still a > > problem. What happens if netback is reloaded against a > > netfront that has already enabled 'feature-xdp'? AFAICT vif->xdp_enabled > > would remain false after the reload. > > in this case xennect_connect() should call talk_to_netback() > and the function will restore the state from info->netfront_xdp_enabled > No. You're assuming the frontend is aware the backend has been reloaded. It is not. Paul